The present invention relates to a novel aldehyde oxidase and, more particularly, to an aldehyde oxidase which catalyzes the oxidation reaction of a substrate aldehyde to the corresponding acid but does not have any catalytic action upon nitrogen-containing aromatic heterocyclic compounds, purine, hypoxanthine and quinine. The invention also pertains to a microbial process for producing this enzyme.
Aldehyde oxidase (EC 1.2.3.1) has heretofore been derived from animal liver such as that of pigs, rabbits, etc., and is known to catalyze the reaction represented by the following equation (1): EQU RCHO+O.sub.2 +H.sub.2 O.fwdarw.RCOOH+H.sub.2 O.sub.2 ( 1)
Aldehyde oxidase of animal origin acts not only upon an aldehyde, but also upon a wide spectrum of various nitrogen-containing aromatic heterocyclic compounds, purine, hypoxanthine, quinines, etc. [J. Biol. Chem., 237, 922(1962), J. Biol. Chem., 239, 2022(1964); J. Biol. Chem., 239, 2027(1964)]. Therefore, it has been reported that those enzymes which have an aldehyde oxidase activity, a quinine oxidase activity and an N'-methylnicotineamide oxidase activity are one and the same protein [J. Biol. Chem., 237, 922(1962)].
Because of the lack of specific substrate activity, use of the known aldehyde oxidase for various purposes has been severly restricted. Accordingly, for commercial application, a need exists for an enzyme which does not suffer from the aforementioned drawback. To this end, it has now been found that certain microorganisms are capable of producing a novel aldehyde oxidase having a different substrate specifically than that of the heretofore known aldehyde oxidase.